Unbalanced nutrition is one of the risk factors leading to life-style related diseases, so it is important to keep nutrition balance adequate, for a healthy life. It is also becoming evident that sufficient intakes of vegetables and fruits have an effective role in improvement of such unbalanced nutrition. In Japan, the targeted daily intake of vegetables is 350 g per day (reference value: 292 g, according to the national nutrition survey in 1997), as recommended by “National Health Promotion Strategy for the 21st Century (Health Japan 21)”. The amount of vegetable consumption, however, is showing a downward tendency after year 1995 when the consumption hit a peak. For instance, the amount of the household vegetable consumption in 1998 is a meager 260 g per day, and the amount of consumed green and yellow vegetables in the same year is a meager 90 g per day. These amounts fall short of the targeted ones. Under such circumstances, it is deemed increasingly important not only to intake crude vegetables, but also to supplementally intake a vegetable juice or the like.
Vegetables or fruits processed into juice have insoluble solids rich in effective components such as carotenoids and minerals. Incorporation of a large amount of such insoluble solids in a beverage could lead to vast numbers of precipitates originated from vegetables and fruits. The formation of such precipitates raised a problem characterized in that insoluble solids containing effective components derived from vegetables and fruits adhere to the wall surface of the beverage container, and such adherents do not easily fall off from the wall surface even by shaking, leading to the impossibility of elimination of said precipitates.
Thus the largest problem with a beverage containing a vegetable juice or fruit juice lies in the fact that a large amount of precipitates is inevitable, so the traditionally existing technologies have centered on prevention of the formation of precipitates.
For example, there is a proposed technology which includes adding agar to a beverage as a dispersing method of insoluble solids contained therein (Patent Document 1). According to this technology, the dispersed state of the insoluble solids in the beverage can be maintained by the addition of from 0.001 to 0.5 wt. % of agar thereto so that the beverage can have a uniform content over the drinking time without shaking or stirring. Nonetheless, this technology has the drawback that even if a uniform dispersed state can be maintained after long-term storage by the use of agar, the beverage inevitably has gel-like physical properties.
There is also a proposed method which includes preparing a jelly drink by incorporating a mixture of gellan gum and pectin or a mixture of agar and locust bean gum as an irreversible gelling agent (Patent Document 2). According to this technology, formation of precipitates can be prevented completely by gelation of the beverage. Nonetheless, such a technology has a drawback in that it becomes a jelly-like beverage and provides palatability utterly different from that of the conventional vegetable beverage or vegetable/fruit mix juice.
There is also a proposed technology which includes using a thickener such as agar, xanthan gum or tara gum for improving the dispersion stability of a bean-curd refuse paste in a bean-curd refuse beverage (Patent Document 3). Although this technology is capable of preventing the formation of precipitates, there is an inherent problem that the mixing amount of the thickener cannot be determined freely because a gelation region appears depending on the mixing concentration.
Thickeners such as pectin, xanthan gum and gelatin are used popularly in order to improve stability of a precipitable food material such as vegetable juice and fruit juice as described above (Non-patent Document 1). They impair the palatability, that is, an important factor in beverage, though having effects on the prevention of the formation of precipitates.    [Patent Document 1] JP-A-7-123934    [Patent Document 2] JP-A-2002-291453    [Patent Document 3] JP-A-2002-51755    [Non-patent Document 1] Food Processing and Ingredients, 31(7), 32-35.